Hundreds gathered in downtown London for a candlelight vigil on Thursday, a day after 52-year-old Khalid Masood killed four people near the British parliament before he was gunned down by police.

The fourth victim, a 75-year-old man who was being treated in hospital, died on Thursday evening.

During the vigil, mourners held a minute of silence for the murdered police officer and former solider, Keith Palmer, as well as the other two victims, American tourist Kurt Cochran and British national Aysha Frade. Another man passed away from his injuries later on Thursday.

London mayor Sadiq Khan commended emergency services in the British capital for their swift response, while also praising the city residents for their courage. Their reaction "showed the world what it means to be a Londoner," he said.

"Londoners will never be cowed by terrorism," Khan said. "Those evil and twisted individuals who tried to destroy our joint way of life will not succeed and we condemn them."

DW's Abigail Frymann-Rouch attended the vigil in London.

'No prior intelligence'

On Wednesday, the British-born Masood drove a rented car into pedestrians at Westminster Bridge, killing at least three and injuring dozens, several of whom are still in critical condition. He than ran through the gates of the nearby parliament building and stabbed the unarmed policeman, before other officers shot him dead.

"Masood was not the subject of any current investigations," police said in a statement after the attack. "However, he was known to police and has a range of previous convictions for assaults, including GBH (grievous bodily harm), possession of offensive weapons and public order offenses."

At one point, the British MI5 intelligence service had investigated the attacker over "concerns about violent extremism," British Prime Minister Theresa May said earlier on Thursday. However, there was "no prior intelligence of his intent or of the plot" the British leader added, describing Masood as a "peripheral figure."

The "Islamic State" militia claimed responsibility for the attack, saying that the attacker was one of its "soldiers." This information has not yet been verified by British officials.

Following the attack, British police launched a series of raids and arrested eight people in London and Birmingham.

dj/kms (Reuters, AP)